There are one hundred and seventy million hepatitis C virus (HCV) carriers or more in the world, approximately 70% of the carriers suffer from chronic hepatitis, who face the risk of hepatic cirrhosis or hepatic cancer. There are approximately two million carriers in Japan as well, and approximately 80% of the carriers have been infected with type 1b.
Interferon therapy is mainly performed as a therapy for hepatitis C. However, a combination therapy where pegylated-interferon α and ribavirin, which is an anti-virus drug, are used in combination has a type 1 virus elimination percentage of 50% or less, a long duration of treatment, and severe side effects, and thus there is a need for the development of a more effective therapeutic drug and the establishment of a therapy.
HCV is a positive-strand RNA virus belonging to the Flaviviridae family, and is constituted by four types of structural protein regions (C-E1-E2-P7) and six types of non-structural protein regions (NS2-NS3-NS4A-NS4B-NS5A-NS5B). Among them, the NS3 protein has serine protease activity on the N-terminal one-third region and RNA helicase activity on the C-terminal two-thirds region. The NS3 protein which has such two activities of protease-helicase has been studied by X-ray crystallography to reveal its conformation (Non-Patent Document 1).
A strong immune response specific to NS3 was observed in patients who recovered from HCV infection (Non-Patent Document 2). Also, the NS3 protein is highly genetically conserved, and many cytotoxic T lymphocyte (CTL) epitopes thereof are identified (Non-Patent Document 3).
Use of a NS3 protein-derived polypeptide for the prevention or treatment of hepatitis C has been reported. For example, Patent Document 1 describes a polypeptide that includes or consists of at least eight-consecutive amino acids derived from amino acids from positions 1188 to 1463 in the NS3 region of HCV, and that includes a T lymphocyte stimulating epitope. Patent Document 2 states that a yeast cell expressing a HCV fusion protein that includes at least a part of a HCV NS3 protease linked to at least a part of the HCV core sequence is used as a base for a vaccine. Patent Document 3 states that a bacterium such as attenuated Listeria monocytogenes that expresses and secretes a full-length protein or an immunogenic protein of NS3 or the like is used as a vaccine platform.
On the other hand, the use of transformed microorganisms by genetic engineering as an oral vaccine has attracted attention. It has been reported that a transformed Bifidobacterium longum expressing flagellin derived from Salmonella typhimurium on the cell surface with a GNB/LNB substrate-binding membrane protein (also referred to as “GLBP” herein), which is present in a cell membrane of microorganisms of the genus Bifidobacterium (also referred to as “bifidobacteria” herein), is orally administered to a mouse so that flagellin-specific antibodies are produced in blood to induce systemic immunity via intestinal mucosal immunity, and the lethal effect of mice due to oral infection with Salmonella typhimurium is effectively inhibited (Non-Patent Document 4 and Patent Document 4). Also, an oral vaccine, which is an acid-resistant capsule preparation containing transformed Bifidobacterium longum that intracellularly expresses, or expresses and secretes flagellin derived from Salmonella typhimurium, Vibrio cholerae, or Shigella dysenteriae, has been reported (Patent Document 5).